Gas release from batteries is controlled with different types of devices in the prior art. Such devices include vent plugs that are used for batteries of vehicles and of stationary drive units. These plugs are provided with a centric opening which, however, cannot avoid an uncontrollable leakage of liquid from the storage battery giving rise to localized corrosion on the outer parts of the accumulator.
WO 99/36976 discloses a device for valve-regulated electric storage batteries that includes a housing to be inserted in an access port of the battery cell. Said housing comprises a lid provided with vents the lower openings, which are closed by a flame arrester fixed in the upper part of an axial opening leading into the battery cell. The lower part of said opening is closed by a valve member formed of a valve body, which includes a pair of opposed vents extending along the lower part of the valve body and defining gas-flow passages from an upstream to a downstream side of the valve body. A series of spaced-apart annular ridges formed on the outer surface of the valve body permit the valve member to be inserted into, and seal by means of a press fit, the inner walls of the housing. The valve member also includes a resilient, radially-outwardly extending annular skirt flaring outwardly in the downstream direction and having an annular free end normally engaging the side wall of the axial opening.
This degassing valve has a rather complicated construction and the sealing element in the form of a resilient skirt may lose, after a certain time, its elastic sealing properties against the cylindrical seat provided in the housing. This will cause hydrogen gas, generated in the cell, to be continuously vented at any internal pressure and to reverse atmospheric pressure from outside to enter the battery at any time.